Rules about the use of prefixes.

1. Prefixes

2. Prefixes are a group of
letters added to the
beginning of a base word
to change its meaning

3. dis honest
prefix Base or root word

4. Prefixes can be
added to
different words
 Verbs
Agree Disagree
 Adjectives
Responsible Irresponsible
 Adverbs
Legally Illegally

5. In this lesson we will
focus on the use of
some prefixes with
adjectives

6. Rules to make opposite
adjectives with prefixes

7. 1. Usually when you
add a prefix you don’t
change the root word.
*notice the double letters
in the following words.
We just add the prefix to
the root word *
dis + satisfied =
dissatisfied
Ir + responsible =
Irresponsible
Im + mature =
Immature
Il + logical = Illogical

8. 2. Use il- before
words starting with I
Legible – illegible,
Legal - illegal.

9. 3. Use ir- before words starting
with r
relevant – irrelevant,
irresistible, irresponsible,
Irregular.
Be careful! There are some
exceptions: real - unreal

10. 4. use im-
before
words
starting with
m, p and b
mature – immature,
immortal, immoral,
immaterial,
perfect – imperfect,
impossible, impartial

11. 5. Another
prefix to make
opposite
adjectives is
un
comfortable – uncomfortable
unfriendly, unlucky,
unhappy.